Environmental Impacts of Renewable Electricity Generation
Fossil-fuel dominated electricity generation in the United States and China has enormous environmental consequences. In 2007, 2.4 billion metric tons of carbon dioxide (CO2) were emitted from electricity generation in the United States, about 40 percent of the country’s energy-related greenhouse gas (GHG) emissions. In the same year, electricity generation in China produced just over 2 billion metric tons of CO2, accounting for about one-third of its energy-related GHG emissions. Fossil-fuel combustion is also responsible for the emission of other pollutants, such as nitrogen oxide (NOx) and sulfur dioxide (SO2). The production of electricity also puts a strain on water and land resources. In 2000, thermal power plants accounted for nearly half of total withdrawals of water in the United States (USGS, 2005) and nearly 40 percent of water withdrawals for industrialized use in China. Overall, reducing environmental impacts is a major impetus for shifting from fossil fuels to renewable energy for electricity generation.
Developing renewable energy technologies that exploit the sun, the wind, and geothermal energy is critical to addressing concerns about climate change and some environmental issues. However, using renewable energy sources will not eliminate all environmental concerns. Although renewable energy sources produce relatively low levels of GHG emissions and conventional air pollution, manufacturing and transporting them will produce some emissions and pollutants. The production of some photovoltaic (PV) cells, for instance, generates toxic substances that may contaminate water resources. Renewable energy installations can also disrupt land use and wildlife habitat, and some technologies consume significant quantities of water.
To develop sound policies, policy makers must understand the relative environmental impacts of alternative energy sources, including how the impacts of renewable energy technologies compare to those of fossil-fuel technologies and to opportunities for improvements in energy efficiency. Understanding the potential environmental impacts of renewable energy technologies is also essential for identifying and pursuing designs, manufacturing methods, project siting, utitlity operations, and so on to mitigate or offset these effects.
Environmental impacts of energy sources are commonly assessed on two scales or levels of aggregation. The first scale is the regional or national scale, which is an attempt to characterize the average impact of a typical facility or installation for the purposes of broad comparisons and planning. Life cycle assessment (LCA), for example, is an attempt to account for the full suite of impacts associated with all stages of an energy project, from the extraction of raw materials to the decommissioning of a facility and the disposal of equipment. The second scale is on the local level, where site-specific impacts, such as effects on wildlife and local water supplies, can be assessed.
The first part of this chapter provides a review of published LCAs as a basis for comparing renewable and fossil-fuel technologies in terms of emissions and energy, land, and water requirements. Detailed LCAs for selected renewable energy technologies are provided in Appendixes B-D of this report. The second half of the chapter provides a discussion of local-scale impacts and permitting and regulatory requirements in the United States and China, with examples illustrating some of the environmental concerns raised by renewable energy projects. Localized effects will warrant more attention as renewable energy deployment accelerates, especially in places where large-scale installations are being considered. The last part of the chapter identifies opportunities for collaboration by the United States and China to advance renewable energy technology by minimizing harmful effects on human health and the environment.
FOSSIL FUEL VS. RENEWABLE ELECTRICITY GENERATION
An LCA estimates resource requirements, energy use, and environmental impacts of products or services at all life stages. The estimates may be derived from detailed, “bottom-up” analyses of mining, manufacturing, transport, construction, operations, and disposal processes or from “top-down” analyses based on national-scale economic input/output models. Overall, an LCA is useful for comparing impacts of different technologies and for identifying points in the life cycle where improvements can be made.
In this section, we present results from published LCA studies compiled by the National Academies Committee on Electricity from Renewable Resources: Status, Prospects, and Impediments (NAS/NAE/NRC, 2010a). These studies provide high-level comparisons of fossil- and renewable-fueled technologies in
terms of net energy production, emissions of GHGs and conventional air pollutants, water use, and land use.
It is important to note that the LCA results presented here were not adjusted for differences in underlying assumptions. Indeed, for renewable energy technologies in particular, the results sometimes depend heavily on the strength and variability of the renewable resource at the assumed site of installation. In addition, newer versions of technologies may produce electricity more efficiently and use cleaner, more efficient manufacturing methods. Differences may also be attributable to differences in geographical location. The NRC committee’s (NAS/NAE/NRC, 2010a) review focused on LCA studies from Europe and the United States, so generalizing the results to conditions in China should be done cautiously. Thus, these LCA results provide a range of estimates that have been published in the literature.
Life Cycle Uses of Energy
An LCA is commonly reported with a net energy ratio (NER), which is defined as the ratio of useful energy output to the grid to the fossil or nuclear energy consumed during the lifetime of the project. For renewable energy sources, NERs are expected to be greater than one, indicating a positive return over the fossil-fuel energy investment. For fossil-fuel and nuclear technologies, NERs are smaller than one and essentially represent the overall life cycle efficiency of the project. NERs are strongly influenced by a number of underlying assumptions, such as plant capacity and life expectancy. For electricity generation from wind and solar energy, the strength of the resource (which will affect the capacity factor of the installed technology) is also a critical assumption. For silicon PV specifically, the NER is highly dependent upon the thickness of the wafer and the efficiency of the cell/module produced.
The highest estimated NERs are generally for wind, followed by biopower and then solar PV (Figure 4-1). Hydropower is also expected to have high NERs, although the results shown in the graph, from a single study, are not as high as anticipated. By definition, NERs for fossil fuels are all less than one, with average estimates of 0.3, 0.4, and 0.3 for coal, natural gas, and nuclear power, respectively. An LCA for a 300 MW solar power tower in Hami, Xinjiang Autonomic Region of China, presented in Appendix B, estimated an NER of 12.4 (in that example referred to as the energy balance factor). Estimates of NERs for three different biomass combustion technologies in China (direct combustion, gasification, and co-firing) are shown in Appendix C. The LCA results for these technologies, which include energy required for biomass cultivation, result in NER estimates ranging from 1.3 for direct combustion to 4.6 for co-firing. Most of the fossil energy used in these cases is associated with energy crop cultivation. NERs would be significantly higher for waste biomass.
Greenhouse Gas Emissions
In 2007, the Intergovernmental Panel on Climate Change concluded that “warming of the climate system is unequivocal …” and that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.” In light of these and other critical concerns about climate change, the United States and China are both taking significant steps to address emissions of CO2 and other GHGs and are weighing further action, including new regulations.
Among the sectors that use fuel directly in the United States, electric power production is the largest source of CO2 emissions, accounting for more than 2.3 billion metric tons in 2007, or more than 40 percent of total energy-related emissions. In China, the electric power sector is estimated to have emitted 3.1 billion metric tons of CO2 in 2007, accounting for nearly half of that country’s total.
Compared to fossil-fuel-based electricity generation, renewable energy technologies offer a major advantage in lower emissions of CO2 and other GHGs. In addition, as shown in Figure 4-2, all forms of renewable electricity production are expected to have significantly lower life cycle GHG emissions (expressed as CO2 equivalents, CO2e) than electricity production from conventional coal and natural gas plants. Supplementing the results shown in Figure 4-2, the solar-power tower LCA in Appendix B estimated GHG emissions of 32 g CO2e/kWh.
Renewable energy would have less of an advantage if carbon capture and sequestration were included with fossil-fuel power plants, or if energy storage systems, such as battery energy storage, compressed air energy storage, or pumped hydro storage, were included as part of renewable energy systems (Denholm and Kulcinski, 2003). We should also keep in mind that there are significant opportunities to improve energy conversion efficiencies and reduce fossil fuel requirements for the manufacture and transport of some renewable energy technologies, especially PV.
GHG emissions for some renewable technologies are difficult to estimate. For example, emissions from biopower vary, depending on which feedstocks are used and the assumptions about their production. Most CO2e values for biopower range from 15 to 52 g CO2e/kWh for biomass derived from cultivated feedstocks, excluding emissions associated with initial land conversion (NAS/NAE/NRC, 2010a). The negative CO2e values shown in Figure 4-2 reflect estimates based on the assumption that biopower could serve as a CO2 sink if waste residues that would otherwise decompose to produce CO2 and methane were used as feedstock (Spath and Mann, 2004). If carbon capture and storage were added to biopower systems, there would also be large reductions in CO2e values.
Similarly, estimates of GHG emissions from hydropower production depend on what is included in the LCAs. Although not reflected in Figure 4-2, some studies have suggested that initial flooding of biomass when a hydroelectric reservoir is filled can release large quantities of CO2 and methane (e.g., Gagnon and van de Vate, 1997). The amount of these emissions depends on the density of the biomass and the size of the reservoir.
Finally, electricity production from closed-loop geothermal systems has low GHG emissions as shown in Figure 4-2 (Hondo, 2005). However, depending on the composition of the reservoir gas, if these gases are vented to the atmosphere, as can occur with flash technology, CO2e GHG emissions can be relatively high. In the worst case, they can approach the emission levels from natural gas combined-cycle power plants (NAS/NAE/NRC, 2010a).
Local and Regional Air Pollution
Electricity generation accounts for significant emissions of local air pollutants in the United States and China. In the United States, the electric power sector
accounts for 18 percent of total NOx emissions and 66 percent of SOx emissions (EPA, 2009). Oxides of nitrogen, which react in the atmosphere to form ground-level ozone, nitric acid, and particle-phase ammonium nitrate, contribute to human health effects, visibility degradation, acid deposition, and eutrophication. Sulfur oxides, which react in the atmosphere to form sulfuric acid and ammonium sulfate, contribute to health effects, visibility degradation, and acid deposition. In addition, coal-fired power plants account for 40 percent of direct mercury emissions in the United States and are believed to dominate direct mercury emissions in China (Wu et al., 2010).
Most renewable energy technologies have much lower life cycle emissions of conventional air pollutants than conventional coal and natural gas plants. For example, the solar power tower LCA in Appendix B estimates NOx and SO2 emissions of only 15 and 43 mg/kWh, respectively. One exception is electricity generation from biomass, which can produce significant NOx, particulate matter, and hazardous air pollutants, such as polycyclic aromatic hydrocarbons (PAHs). Although biomass has lower nitrogen content than fossil fuels, a substantial quantity of NOx is formed whenever high-temperature combustion occurs in air, through oxidation of atmospheric nitrogen (N2) at high temperatures (see Figure 4-3). Although direct emissions of NOx and SOx are expected to be low for geothermal power plants, flash and dry-steam geothermal facilities can produce significant quantities of hydrogen sulfide (H2S) from geothermal reservoirs, unless steps are taken to abate it (DiPippo, 2008).
For other renewable technologies, life cycle emissions of conventional air pollutants are mainly from the manufacturing or construction stages of the life cycle. As discussed below for PV, emissions during manufacturing depend strongly on how efficiently energy is used in the manufacturing process and the efficiency and degree of pollution control at the manufacturing site.
Land and Water Use
Land is in limited supply in many parts of the United States and China. Hence the physical footprint of new facilities and feedstocks for electrical generation is an important consideration. In additional, the amount of land used is a rough proxy for other impacts of new development, including impacts on ecosystems, cultural and historical resources, scenery, and agricultural land.
When the impacts on land use are measured simply by the surface area they occupy during their life cycle, some renewable energy technologies appear to have heavy land-use requirements (Figure 4-4). However, this approach does not take into account the intensity of land use or whether the technology allows for simultaneous use of land for other purposes. Whereas coal-fired power plants fully occupy the sites where they are constructed, small-scale PV installations may be placed on rooftops where they cause little or no interference with the
primary use of the land for commercial or residential buildings. Thus, smaller scale or distributed solar technologies may have less of an impact on land use and habitat loss than large-scale, central station plants. Land-use concerns may also be addressed by deploying renewable energy systems on previously developed sites, rather than in undeveloped areas (Mosey et al., 2007).
The high land-use requirements for biopower shown in Figure 4-4 assume that the feedstocks have been cultivated for energy production; if waste biomass is used as the feedstock, the land-use impacts are significantly lower. In China, the biomass materials likely to be used for electricity generation are mainly agricultural residues (e.g., straw, bagasse, and rice husks), forestry wastes (e.g., wood chips, sawdust, and bark), and municipal solid waste. Plants grown for energy are expected to comprise a very small proportion of biopower feedstocks in China.
The potential of waste resources available in China is estimated at about 370 million tons of coal equivalent (Tce), equivalent to about 14 percent of total Chinese energy consumption in 2007. Incremental land-use requirements for using waste materials as biopower feedstocks are insignificant. Moreover, if not used for biopower, some waste resources, such as municipal solid waste, would otherwise occupy land and could cause environmental damage if not disposed of properly.
The hydropower estimate shown in Figure 4-4 represents land use for the Glen Canyon Dam and Lake Powell, attributing the full area of the reservoir to electricity generation (Spitzley and Keoleian, 2005); in contrast, small-scale hydropower and run-of-the river installations would have minimal land-use requirements. Land-use requirements for electrical transmission and distribution lines and facilities, which are significant for all centralized electricity generating facilities, are not shown in Figure 4-4.
Water is a scarce resource in large portions of the United States and China. Recent global circulation model projections suggest that, if climate change proceeds as expected, under current business-as-usual scenarios, freshwater supplies will become even scarcer in some parts of the United States (Milly et al., 2005). In China, the amount of water available per capita is 2,200 m3, only a quarter of the world per capita average. Water supply problems in China have been exacerbated because the spatial distribution of water is very uneven.
Electricity production using thermoelectric technologies requires vast amounts of water, primarily for cooling. In the United States, about 43 percent of existing thermoelectric generating capacity uses once-through cooling, 42 percent uses recirculating wet towers, 15 percent uses recirculating cooling ponds, and 1 percent uses dry cooling (Feeley et al., 2008). Water use by power plants is characterized by withdrawals (the total amount of water taken from a source) and consumption (the amount of water not returned to the source). Although consumption is sometimes emphasized over withdrawals, the latter is important, because power plant operation may be constrained by the amount of water available for withdrawal and power plant uses may compete with other demands for water (Gleick, 1994). Furthermore, water returns can be significant sources of thermal pollution and may include discharges of chemical pollutants, such as chlorine or other biocides used in cooling towers.
The U.S. Geological Survey estimates that nearly 280 billion cubic meters (BCM) of water was withdrawn in 2000 for thermoelectric power generation in the United States, accounting for nearly half of total withdrawals (USGS, 2005). Water consumption by thermoelectric facilities in the United States is much lower, an estimated 4 BCM in 1995 (estimates for 2000 are not available), but this quantity nevertheless constitutes more than 15 percent of U.S. water consumption for uses other than irrigation (Feeley et al., 2008). Water use by thermoelectric plants in China is also huge. In 2006, the quantity of withdrawals was 49 BCM, accounting for 37 percent of total industrial use. Chinese thermoelectric plants consumed an estimated 7 BCM of water.
Water consumption by geothermal plants depends on the technology and geothermal resource, as well as the cooling system. The 2,000 gal/MWh water requirement shown in Figure 4-5 reflects experience in the Geysers geothermal
resource area in California, where a dry-steam system withdraws 2,000 gal/MWh from the geothermal field, with 70 percent of the water consumed in an evaporative tower (Hall et al., 2006). The balance of water, for recharging the reservoir, comes from secondary-treated wastewater from a nearby community (DiPippo, 2008). Water consumption in liquid-dominated binary geothermal systems can be very high if wet cooling towers are used, but can be much lower if hybrid or air-cooled systems are used.
Wind and solar PV technologies use very little water. Water-use requirements for solar thermal plants also depend on the cooling system. Values shown in Figure 4-5 reflect operating experience with a 350 MW parabolic-trough system in the Mojave Desert, which uses evaporative cooling and consumes about 800 gal/MWh; a comparable estimate of water consumption for solar power tower technology; and a projection of negligible water consumption with an air-cooled parabolic dish system.
Finally, if evaporative losses from hydroelectric reservoirs are ascribed fully to the generation of electricity, large-scale hydroelectric power can be considered to consume more water per MWh electricity output than any other electricity generation technology (Gleick, 1994). However, reservoirs associated with hydroelectric power plants may have other uses, such as storage of irrigation water. Thus, evaporative losses may not be exclusively attributable to electricity generation.
Life Cycle Assessment of Solar Photovoltaic Technology
Although thin-film cadmium telluride and amorphous-silicon technologies are gaining ground in the global marketplace, most PV panels produced today are made of single or multicrystalline silicon. As discussed in Appendix D, in China, the production of high-purity polysilicon for solar cells is a rapidly growing industry, although it has high energy requirements and serious pollution problems at some facilities. To minimize these impacts, polysilicon manufacturers in China, as elsewhere, must use state-of-the-art methods to reduce energy consumption and address problems with hazardous materials and wastes. In response to these environmental concerns, especially the need to separate and recycle tail gas, China has initiated a key research project on the comprehensive use of by-products from polysilicon production.
As indicated above, although life cycle impacts of solar PV are estimated to be much lower than those of electricity generation from fossil fuels, the estimated NER and emissions impacts of PV are somewhat less favorable than for wind technology. The main reason is that production of PV panels is very energy intensive, with significant associated emissions of CO2, NOx, and other air pollutants.
Estimates of energy requirements for silicon PV panel manufacturing vary widely, depending in part on the vintage of the manufacturing technology and in part on the sources of process heat and electricity required. Alsema (2000) reported that estimates published up to that time ranged from 2,400 to 7,600 MJ m-2 for
multicrystalline silicon and from 5,300 to 16,500 MJ m-2 for single-crystal silicon panels. To illustrate the distribution of energy requirements among the steps in the process, Figure 4-6 shows a breakdown for manufacturing of multicrystalline silicon PV modules, beginning with the production of metallurgical-grade (M-g) silicon. The fractions shown are adapted from estimates by Alsema (2000) and Alsema and de Wild-Scholten (2006). Alsema and de Wild-Scholten (2006) assumed the polycrystalline silicon is produced in part using the Siemens process and in part through a modified Siemens process, with an overall average electricity requirement of 110 kWh/kg Si and assuming 1.67 kg Si is used per square meter of PV panel. Whereas Alsema and de Wild-Scholten assumed electricity for polysilicon production was supplied from a mixture of hydroelectric and natural gas combined-cycle generation, the modified results shown here were calculated assuming electricity used at all stages in the process was produced from primary fuel with a net conversion efficiency of 31 percent. The overall estimate of the energy requirement is in the middle of the range cited by Alsema (2000). The results show the importance of electricity used at the silicon-purification stage.
If the silicon is purified using inefficient processing technology, electricity is supplied from relatively inefficient power plants, or polycrystalline silicon is wasted in wafer production steps, energy requirements can easily exceed those shown. By the same token, at some production facilities, the fossil energy required for polycrystalline silicon production has been greatly reduced by process improvements,
including fluidized bed reactors for the silane decomposition step and renewable or highly efficient electricity sources.
The process of manufacturing PV panels also entails the use, or by-product production, of a number of hazardous materials that must be monitored, handled, and disposed of properly to minimize risks to workers, the public, and the environment. In addition to SiCl4, these substances include silane, a highly flammable intermediate of polysilicon production, and hydrofluoric acid (HF) and other toxic gases and acids used in cleaning silicon wafers and in texturing and etching. Large amounts of acidic and alkaline wastewater are produced, so wastewater treatment and acid recycling are also critical steps.
Fluoride in wastewater poses special problems, because an excessive amount of fluoride in drinking water can cause a variety of diseases. Thus, strict standards are necessary to regulate the treatment and discharge of water containing HF. These issues are discussed in more detail in Appendix D, where research for reducing environmental and health and safety issues associated with polysilicon manufacturing are highlighted.
PROJECT-SCALE IMPACTS AND REGULATION FOR RENEWABLE ENERGY
Renewable energy facilities, like other means of electricity production, can have significant environmental and socio-cultural impacts. Depending on the technology, location, and scale of the facility, these impacts can include soil erosion or degradation, forest clearing, disturbance or loss of wildlife, air and/or water pollution, noise pollution, and impairment of scenic vistas. For renewable technologies, these impacts are often, but not always, similar to or milder than the effects of other industrial development on a similar scale. Nonetheless, locating renewable energy projects in sensitive areas can make the environmental licensing of the project difficult and more costly, and so these project-scale impacts can affect the rate of deployment.
Assessments of Ecological, Aesthetic, and Cultural Impacts
Among renewable electricity technologies, large-scale hydroelectric projects have historically had especially stark consequences, especially if they involved flooding scenic valleys or town sites. For example, when the Dalles Dam on the Columbia River was completed in 1957, the associated reservoir flooded Celilo Falls and the village of Celilo, a tribal fishing area and cultural center that archeologists estimated had been inhabited for millennia (Oregon Historical Quarterly, 2007). Like other dams on the Columbia River, the Dalles Dam serves multiple purposes, including improved navigation, irrigation, flood control, and the generation of nearly 1,800 MW of electricity. Although the Dalles Dam has provided
widespread benefits, they came at great cost to the Native Americans whose community and traditions were rooted in the area (Wilkinson, 2005).
Since the Dalles Dam was completed, a web of U.S. laws have been enacted to protect natural and cultural resources from development pressures. These include the 1964 Wilderness Act, which prohibits activities that damage the character of wilderness in specified areas, the 1968 Wild and Scenic Rivers Act, which bans construction of dams and associated hydroelectric projects on protected stretches of rivers, and the 1969 National Environmental Policy Act (NEPA), which requires that environmental reviews be completed with full opportunities for public input before federal actions are taken. In part because of these protections, the pace of large-scale reservoir construction in the United States has slowed dramatically since the 1970s, and most new U.S. efforts to develop hydroelectric power plants are likely to be relatively small-scale systems. At the same time, however, as plans for utility-scale wind and solar projects move forward in the United States, advocates will have to take great care in siting and designing projects and operations that minimize environmental and social costs.
A case in Hawaii is another example of controversy surrounding the siting of renewable energy projects in locations of natural, cultural, or religious value. In 2007, Hawaiians celebrated the protection of a 26,000 acre tract of lowland rainforest on the island of Hawaii, after more than 20 years of efforts to restore public access and block the development of a geothermal power plant at the site (OHA, 2007). In the late 1980s, True Geothermal Energy Co. secured a permit to develop a 100 MW geothermal plant in the then privately held Wao Kele O Puna rainforest (Boyd et al., 2002). Native Hawaiians opposed the development because they traditionally used the area for hunting and gathering and for religious purposes. Some native Hawaiians also objected to the exploitation of geothermal resources in general because of reverence for Pele, the goddess of volcanoes in the native Hawaiian religion. The Wao Kele O Puna geothermal project was abandoned in 1994.
When the land was subsequently offered for sale, the Pele Defense Fund, a native Hawaiian group, approached the Trust for Public Land to arrange a purchase for conservation purposes. Only one geothermal power plant—the 30 MW Puna Geothermal Ventures Plant—is currently operating on Hawaii. As the Hawaiian Electric Company moves forward with plans to increase development of geothermal and other renewable resources in the state, it has recognized the need to deal with cultural and environmental concerns in advance “with openness and respect.”1
Impact on Wildlife
After hydropower, whose impacts have been fairly well documented (e.g., ORNL, 1993), impacts on wildlife have been a particular concern for wind energy. Collisions with wind turbines have killed birds and bats; the numbers depend in
See the “Environmental and Cultural Concerns” page of HECO’s website, http://bit.ly/9GKmwb.
part on turbine technology and, very strongly, on turbine siting. In the United States, wind turbines were estimated to have killed roughly 20,000 to 40,000 birds in 2003 (NRC, 2007). Although these totals are much smaller than the hundreds of millions of bird deaths nationwide attributed to collisions with buildings, high-tension lines, and motor vehicles, localized impacts on specific bird populations can be significant. For example, raptor fatalities at the Altamont Pass wind site in California in the 1980s caused significant concerns.
Relatively limited data on bat deaths from wind turbines are available, but mortality rates at some facilities are as high as 40 recovered carcasses per MW per year (NRC, 2007). The significance of this rate of bat deaths is hard to gauge, in part because of a lack of baseline data on species’ abundance. However, ecologists warn that as wind energy development accelerates in the United States, the potential for biologically significant impacts on bats is a major concern (Kunz et al., 2007).
In the past decade, the wind industry in the United States has been required to pay more attention to siting considerations and equipment modifications to reduce animal mortality rates. The Fish and Wildlife Service (FWS, 2003) has issued interim guidelines for minimizing the impacts of wind projects on wildlife, and an effort to revise and update them is currently under way.
These concerns are embodied in substantive laws that can go beyond imposing procedural requirements (as NEPA does) to sharply curtail or block development in some areas. The Endangered Species Act (ESA) of 1973 is a prime example; this law requires that federal agencies “insure that any action authorized, funded, or carried out by such agency… is not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of [critical] habitat…” (16 U.S.C. §1536(a)(2)). ESA further prohibits any person from “taking” any endangered species or listed threatened species of fish or wildlife (16 U.S.C. §1538(a)(1)) where “take” is broadly defined to mean “harass, harm, pursue, hunt, shoot, wound, kill…” (16 U.S.C. §1532). ESA requires consultation with the Fish and Wildlife Service before initiation of projects that require federal action. Even for project development on private lands, consultation is recommended to avoid incidental harm. If there is a potential for incidental harm, project developers may proceed by securing an incidental take permit, which typically entails developing and implementing a habitat conservation plan and appropriate mitigation measures.
Aesthetic concerns may not be specifically regulated but can be a significant issue for communities where new renewable energy projects will be located. The NRC (2007) study of environmental impacts of wind energy notes that in many countries and cultures, people form strong attachments to the place where they live that influence their reaction to new developments. Wind farms in particular
are often proposed for ridgelines and other locations with a high density of wind where turbines are highly visible. Moreover, as with other renewable energy facilities, they are often proposed for locations where there has been no prior industrial development. The NRC (2007) study recommends a visual impact assessment process for determining whether a particular wind project would result in undue harm to valuable aesthetic resources and cautions that meaningful public involvement is crucial for acceptance. These same concerns would apply for transmission lines as well, and thus could become an important factor in the acceptability of large-scale renewables projects requiring new transmission.
Procedure in the United States
Under NEPA (and similar state laws), federal (or state) agencies must assess in advance the environmental impacts of their actions. Actions that fall under NEPA requirements range from the provision of loan guarantees for renewable energy projects to the granting of rights-of-way or the issuance of leases for construction of projects or transmission lines on or across federal lands. The objective of NEPA is to ensure that agencies fully consider potential environmental impacts and allow all interested parties, including the public, to provide input into the process before decisions are made.
The process typically begins with a brief Environmental Assessment (EA), the purpose of which is to determine whether the activity might impose a significant environmental impact. If so, the agency must prepare a full Environmental Impact Statement (EIS); if the agency anticipates little or no environmental impact, a Finding of No Significant Impact (FONSI) is issued. The majority of projects proceed with an EA, often after agreement has been reached on mitigation measures, and do not require full-blown EIS documents. However, large projects usually require a full assessment.
In recent years, the Bureau of Land Management (BLM), under the U.S. Department of Interior, has collaborated with the U.S. Department of Energy (DOE) to complete region-wide “programmatic” EISs for wind energy development (BLM, 2005) and with the U.S. Department of Agriculture Forest Service for geothermal energy development in the western United States (BLM, 2008). BLM is currently working with DOE on a programmatic EIS for utility-scale solar energy projects (DOE, 2009). BLM assessments are important because the agency administers more than 260 million acres of public land in the United States, almost all of it in the western half of the country and much of it rich in renewable energy resources.
Each programmatic assessment addresses the implications of broad policies designed to facilitate private development of renewable energy on federal lands. EIS studies examine potential environmental, social, and economic impacts on a broad scale, with the objective of assessing resource potential; identifying lands
that should be categorically excluded from leasing; identifying best practices for mitigating impacts; and developing guidelines for public involvement and consultation with other agencies during subsequent project-level reviews of site-specific proposals.
As an example, the programmatic EIS for wind identifies potential impacts on soils; water resources and water quality; air quality; noise; vegetation; wildlife; paleontological resources; and cultural resources, including sacred landscapes, historic trails, and scenic vistas (BLM, 2005). Impacts on soil, water, and air quality are expected to occur principally during project construction, whereas impacts on noise, wildlife, and scenic vistas are expected to continue throughout the life of the project. Programmatic analyses have helped to streamline later assessments of individual projects but cannot supplant case-by-case analysis because impacts on natural and cultural resources are usually site specific.
Procedure in China
The Environmental Impact Assessment Law of 1979 mandates that a developer complete an environmental assessment before project construction. If not, the developer is required to complete a post-construction assessment. The Environmental Protection Bureau can fine the developer approximately $25,000 if no assessment is completed for the project. In recent years, numerous environmental disputes have arisen over the construction of waste incineration power plants. For example, protests by nearby residents against the construction of the Liulitun waste incineration power plant in Beijing had a significant social impact at the time. Since then, a mechanism for public participation has been introduced. For controversial projects that are environmentally sensitive, local governments are responsible for explaining the project to the public and for holding public hearings, if necessary.
Overview of Environmental Planning and Permitting
Planning and Permitting in the United States
Like other economic sectors, the electric power sector (generation, transmission, and distribution facilities) in the United States is covered by a wide range of land-use and environmental regulations that encompass the development and construction of new facilities, facility operation, and decommissioning and site restoration. Project developers must typically attend to layers of local, tribal, state, and federal regulations and deal with multiple agencies and permitting processes. Different project developers may be involved in the generation facilities and in the transmission/distribution facilities. Thus the complexities of planning and permitting may be multiplied in terms of approval steps and timelines due to the number of parties involved. Special protections or bans on development may apply to lands (including privately owned land) with special designations, including historic sites, prime farmland, and wilderness and roadless areas. Where federal
or state action is required for project development, NEPA or parallel state laws require environmental review as part of project planning.
Federal NEPA requirements apply for any electrical generating facilities or transmission lines on federally managed public lands or offshore. Approximately 30 percent of the land in the United States is federal public land, and public lands are especially prevalent in the western United States, where significant wind, solar, geothermal, and hydropower resources are located.
The American Wind Energy Association has compiled a guidance document that outlines the types of local-scale environmental impacts that can arise and the corresponding regulatory framework that governs the development of wind energy projects (AWEA, 2008). Projects developed on private lands face an array of local, tribal, state, and federal land-use and environmental review and permitting requirements designed to ensure that potential impacts are identified and mitigated.
Siting and land-use regulations for privately owned land are usually the purview of state, tribal, or local governments, and hence vary widely across the country. In some states, public utility or state energy siting boards have jurisdiction to review and authorize new electricity generation facilities. State environmental quality and wildlife conservation agencies may implement requirements for environmental review. In other states, or for relatively small projects, siting decisions may be left to municipal or county agencies. Whether or not state-level approval is required, almost all projects on private land require local review for compliance with zoning restrictions and ordinances limiting height, setbacks, and noise.
Renewable energy projects that release contaminants into air or water or thermal pollution to surface bodies of water may also be subject to state and federal regulations. The primary laws governing air and water pollution in the United States are the Clean Air Act and Clean Water Act, both of which include direct federal regulations as well as programs that are mandated and enforced by the federal government but administered by states or tribes. Compliance with air pollution regulations under the Clean Air Act is required for biomass combustion and geothermal facilities that release pollutants to the atmosphere during operation; other renewable projects that entail clearing land or construction of new roads may also have to address concerns about vehicle or construction equipment emissions and fugitive dust. Biomass, geothermal, and solar thermal power plants that discharge cooling water to lakes or rivers face regulation for thermal pollution as well as contaminant discharges. Discharge permits may also be required for renewable energy projects that use water during exploration or production phases, including for sanitation and dust suppression.
Planning and Permitting in China
Confronted with multiple pressures, such as the need for economic development, expanded employment, and mitigation of GHG emissions, the Chinese government has promulgated policies and implemented laws on energy conserva-
tion, environmental protection, and sustainable development (see Chapter 5 for details of specific policies). However, to avoid or mitigate environmental, cultural, ecological, and scenic impacts, the development of renewable energy projects is subject to other national laws and regulations.
Specifically, projects that involve feed-in power generation from renewable energy must secure administrative permits and submit information in conformance with relevant laws or provisions of the State Council. Western China, for example, is the birthplace of Chinese civilization. Throughout history, people of many nationalities have developed and created a rich and valuable cultural heritage, and artifacts in the region are the historical testimony that people of all ethnic groups developed the region and lived there together. To protect the cultural relics in these areas, on August 31, 2000, the State Council issued the “Notice of General Office of the State Council on reinforcing cultural relic protection and management in west development by the General Office of the State Council” (No. 60 in 2000).
Since the adoption of the Renewable Energy Law, additional environmental regulations have appeared in China specifically to address environmental impacts of biomass power generation. In 2006, the State Environmental Protection Administration (now MEA) and National Development and Reform Commission (NDRC) promulgated an official document to strengthen the environmental evaluation and management of biomass power generation projects. In accordance with the new provisions, the construction and operation of waste incinerators must meet national or industry standards (such as GB13271-2001 Solid Waste Incineration Pollution Control Standard), and the quantity and quality of garbage must be guaranteed. At present, to qualify as a biomass power generation project, the proportion of conventional fuel fed into the furnace by mass must be limited to 20 percent when a fluidized bed incinerator is used to deal with solid waste. In addition, existing laws, such as the Thermal Power Plant Air Pollutant Emission Standards (GB13223-2003) and Boiler for Air Pollutant Emission Standard (GB13271-2001), regulate emissions.
Although laws and codes issued by the Chinese national government are considered to be the dominant set of rules, because of China’s vast territory and numerous regional differences, implementation of a particular project on a local scale can differ from centrally established guidelines. Some local governments faced with economic development pressures, a lack of modern technology, and a shortage of capital have been lax in implementing or enforcing laws and codes, although this situation is improving. Lessons from the experience of developed countries and increased capital investment can further improve the implementation of standards. As public awareness of and interest in environmental issues increases in China, there are likely to be projects that attract public opposition.
In comparison to fossil fuels, renewable sources of electricity such as solar, wind, and geothermal can offer substantial environmental benefits, especially with
regard to GHG emissions. When life cycle emissions are considered, all forms of renewable electricity production are expected to have significantly lower GHG emissions per unit of electricity produced than generation from conventional coal and natural gas plants. With the exception of emissions of NOx and carbonaceous materials from biomass combustion, rates of life cycle emissions of conventional air pollutants from renewable electricity generation are also sharply lower than from coal and natural gas plants.
Although renewable energy sources have major advantages over fossil fuels, they also raise some environmental concerns. Many renewable energy technologies are ready for accelerated deployment, but research and development are still needed to reduce their environmental impacts. While wind, solar PV, and some geothermal plants have very low water requirements, biomass, concentrating solar thermal, and some geothermal plants generally have requirements comparable to those of other thermoelectric facilities. The United States and China would benefit from efforts to further improve cost effectiveness and efficiency of low water-use cooling systems to help expand their utilization. Also, as a result of evaporation, water consumption associated with large-scale hydropower plants and other uses of associated reservoirs is particularly high.
LCA is a valuable method of comparing environmental impacts of alternative electricity generating technologies and identifying where improvements are most likely to pay off. LCA shows that increasing system efficiencies and operating lifetimes will reduce environmental impacts for all renewable energy technology. The life cycle GHG emissions benefits of renewable energy are generally high, but improvements are possible in some areas. In particular, research and development are needed to reduce life cycle GHG emissions for emerging storage options, such as batteries and compressed air energy storage, and to reduce GHG emissions and electricity use in PV manufacturing.
To minimize waste in the modified Siemens process for polycrystalline silicon production, the toxic silicon tetrachloride (SiCl4) produced as a by-product of trichlorosilane decomposition must be recycled. Several tons of SiCl4 are produced per ton of polysilicon, and unless it is recovered and sold as a by-product or recycled in the polysilicon production process, a large share of the silicon feedstock is wasted. However, because the components of the tail gas are very complex, separation and recycling are difficult. News reports (e.g., Cha, 2008) indicate some Chinese polysilicon producers have not been attempting this critical step. Additional research is needed on the life cycle impacts of thin-film technologies, which comprise different processes and inputs than silicon flat-plate PV (Fthenakis, 2009).
Both countries will need to reduce air pollution emissions from biomass combustion. As shown in the LCA section of this chapter, the majority of energy consumption and emissions associated with biomass power generation is in the plant cultivation stage. Both the United States and China are currently focusing on using waste biomass and should continue to do so. Even with waste biomass,
however, pollutants are emitted during plant operation. Pollutants associated with the combustion of biomass include PAHs and nitrogen and SOx. The combustion of municipal solid waste can produce dioxins and release heavy metals that must be captured.
Biomass has lower nitrogen content than coal, but it also has lower heating values (15 to 21 MJ/kg for biomass compared to 23 to 35 MJ/kg for coal). Therefore, some biomass fuels can produce more NOx emissions than coal does for the amount of heat it produces. The production of NOx from the nitrogen in biomass is not well understood, because the forms of nitrogen are different from those in coal. Therefore, research is needed to minimize pollutant emissions during biomass power generation processes.
Land use is also a significant issue with some renewable energy technologies, especially as we envision scaling them up in the future. Research will be necessary to understand the impacts that renewable power installations have on plants and wildlife in various geographies, and to develop effective ways to mitigate these impacts. Land-use impacts can be reduced by the use of previously developed sites, co-occupation with other land uses, using military and government sites, and encouraging distributed generation technologies to minimize the need for more transmission lines. Renewable power development will have to be restricted in areas with sensitive ecosystems or high cultural or scenic value, and public involvement will be invaluable for helping to identify these areas. Additional research is also needed to understand impacts of large-scale (e.g., 10 MW for PV, 100 MW for wind) renewable energy installations on meteorology and climate.
It is evident that, in both countries, large-scale renewable energy installations will also require new transmission infrastructure that entails environmental impacts. Siting and constructing new transmission requires similar processes, in terms of impact assessments, licensing, and permitting. Project developers may need to plan for this up front, and work with regulatory agencies, environmental and civil society groups, and transmission utilities to identify ways to mitigate transmission impacts. Opportunities include: identifying areas of common transmission corridors for use by a number of projects, addressing the need for new substations for interconnection and power transmission, and enlisting local support for transmission projects that enable more renewable energy technologies to be deployed.
Finally, recognizing that renewable energy facilities and the installed generation technologies will have a finite lifespan, both countries will have to pay more attention in the next decade to decommissioning, recycling, disposal, and site restoration.
Scientists and engineers in both countries should work together to solve key technical challenges in waste treatment and recycling of components. Opportunities include reducing or reusing silicon tetrachloride and other toxic byproducts of polysilicon production, and recycling PV panels and wind turbine blades.
For biomass power generation, the priority should be on reducing combustion emissions and using available waste resources (rather than dedicated energy crops), including municipal solid waste and agricultural residues.